1. Field of the Invention
The present invention relates to an irradiated power monitoring system for optical fiber for use in laser working apparatus or laser surgical operation apparatus.
The present invention particularly concerns an irradiated power monitoring system for optical fibers having high reliability without interrupting laser working or laser surgical operation.
2. Description of the Prior Art
The conventional laser working apparatus or laser surgical operation apparatus utilizing a laser beam of a CO.sub.2 laser have used mirror joint waveguide means for guiding the laser beam from the laser oscillator to an object working point. However, the mirror articulated waveguide has problems such as, the deviation of light beam from the designated path due to vibration of the mirrors and arms or inconvenience of handling. Accordingly, in order to solve such problems in the conventional laser working apparatus or laser surgical operation apparatus, use of optical fibers as a laser beam waveguide has been tried. FIG. 1 shows the inventor's experimental apparatus using the optical fiber as the laser beam waveguide in a schematic way. Laser light beam 5 emitted from the laser oscillator 1 is converged by a first converging lens 2 to produce a converged light beam 6 which is input to an optical fiber 3. The light beam issued at the output end 3a of the optical fiber 3 is focused by a second converging lens 4 so as to produce a focus point 8 to be applied on an object, which is a work piece to be worked or an affected part of a patient to be operated.
In such laser beam working apparatus or laser beam operating apparatus, the energy of the light beam focused by the second lens is directly utilized; thereby, it is necessary to monitor the level of the focused laser light. The above-mentioned way of monitoring the laser output power has been made by measuring the current of the laser oscillator tube and calculating the output power using that measured current. Another way of monitoring is made by providing a movable mirror between the output end of the laser oscillator and the first focusing lens, when measuring laser power, thereby reflecting the laser light by the mirror and give it to a laser power detector. Both of the above-mentioned monitoring means only monitors the output power of the laser oscillator and not the laser power to be irradiated on the object 8 from the hand piece 9.
When an optical fiber is utilized as a laser light waveguide in a laser light working apparatus or laser light operation apparatus, the output power of the laser light is as large as, for instance, 40 W or sometimes more, and such high power laser light will considerably heat the optical fiber, thereby the optical fiber is liable to deteriorate or age as time lapses. Thus, the laser light output from the hand-piece will decrease as time lapses while the output power from the laser oscillator does not decrease as much. Furthermore, when the optical fiber is broken at the midst thereof, the light beam is not irradiated from the hand-piece at all, while the monitored output level based on the above-mentioned measurement does not change. Therefore, the laser light output monitoring at the end of the laser light oscillator 1 does not constitute a reliable monitoring system. When the laser light power is monitored by providing the mirror to guide the laser light to the detector, the laser light is reflected by the mirror and is not inputted to the optical fiber. Therefore the above mentioned monitoring method is neither convenient nor reliable.